I used TI's models.

http://www.edn.com/electronics-blog...ce-simulation-Tina-TI-LTSpice-PSpice-and-more is Paul Rako's blog from a couple of years ago. The comment section is also a good read.

Here's how I would do the circuit ...

Too much symmetry,Joe.
Comparator U2 has negative feedback.

 

Thanks for pointing that out Ron